In the present specification, sugars, lipids and binding manners thereof will be described in such a manner as generally or commonly employed in the art.
Glycolipids have attracted public attention in particular in the field of differentiation and carcinogenesis of cells. In the studies on glycolipids, not only conventional biochemical processes but also immunochemical processes with the use of an antibody specific to each glycolipid have been frequently employed in identifying, determining and purifying the same. Since the techniques for the preparation of monoclonal antibodies developed by Kohler and Milstein have been generalized, it is essential to use monoclonal antibodies in studying glycolipids. However there are many glycolipids commonly observed in animals which are usually used in various experiments. In these cases, immunization among these animals can not bring about the development of any antibody in the blood, which makes the preparation of monoclonal antibodies impossible.
Further, even if immunization can be established in an animal, it is difficult to prepare a monoclonal antibody if antibody-producing cells, which will be also referred to as immunocytes hereinafter, of said animal can not play a satisfactory role as a partner of myeloma cells conventionally used in the preparation of hybridoma cells. Glycolipid GAl is an example thereof. Namely, GAl is present in the tissues and on the cell surfaces of a mouse, a rat and a normal man but absent in a rabbit. Therefore an antibody against GAl is normally obtained by immunizing a rabbit. However it is frequently observed that antibody-producing cells of a rabbit can not be a desirable partner of myeloma cells of a mouse or a rat. Thus there has been no report of success in the preparation of a monoclonal antibody against GAl.
We have studied in order to prepare an antibody against a substance which is present in a mouse, a rat and a man in a normal state, i.e., a constitutent per se. As a result, we have succeeded in the preparation of a monoclonal antibody agaisnt GAl, which is a constituent of a rat and a man, by selecting an animal which exhibits a relatively high immune response to a material of a low immunogenicity, thus completing the present invention.
Further we have assayed GAl concentration in the sera of human patients suffering from cancer with the use of a monoclonal antibodies against said GAl and consequently found that the GAl concentration in the blood of a cancer patient is higher than those of normal men or those suffering from benign diseases regardless of the type of cancer.
Taki et al. have reported on the diagnosis of cancer through the assay of the GAl concentration in blood with the use of anti-GAl antibody (cf. 43rd Proceedings of the Japanese Cancer Association, p. 418 (1984)). In the above report, they used a polyclonal anti-GAl antibody purified from an antiserum obtained by immunizing a rabbit with GAl.
It is believed that a method for detecting a glycolipid with the use of a polyclonal antibody thereto is not completely reliable in its accuracy when compared with the one wherein a monoclonal antibody is used. Therefore the diagnosis of cancer with the use of the monoclonal anti-GAl antibody of the present invention is superior.
Thus the monoclonal anti-GAl antibody of the present invention is highly useful not only in the basic studies on glycolipids but in the diagnosis of cancer.